The present invention relates to cellular telephone communications and accessories therefor, and more particularly, to an electronic device for blocking cellular communications in a designated space, such as public institutions, theaters, etc.
The proliferation of portable cellular telephones has given rise to a new cultural phenomena, visible and audible in many social settings, and public gathering places, institutions, and the likexe2x80x94ringing wireless telephones and open conversations. Depending on the locale and the type of setting, this phenomena has become an intrusion at best, and at worst, it has become very annoying to others engaging in quiet discourse, or seeking peace.
Therefore, there is a recognized need for a device which will prevent the ability to establish a cellular telephone conversation, either received or initiated, in a given area. This need derives from security-related, cultural and other norms.
Cellular communications are provided by mobile telephones in vehicles, or by personal cellular systems (PCS) and by multiple cell networks. Several different methods exist for establishing cellular communications, with differences in frequency range, modulation, signal processing, compression, bandwidth, demodulation and signal detection, etc.
Examples of existing cellular communication methods include:
AMPS/TACSxe2x80x94Analog
NAMPS/NTACSxe2x80x94Narrow AMPS/TACS (IS 91/88)
TDMAxe2x80x94Time Division Multiple Access (IS 54/136)
GSMxe2x80x94Global System Mobile (IS 95)
CDMAxe2x80x94Code Division Multiple Access
FDMAxe2x80x94Frequeny Division Multiple Access
The frequencies of operation of some of these methods are listed in the attachment drawing Table 1.
The common denominator in all of these methods and techniques is based on predetermined control frequencies, to which the cellular units are directed or xe2x80x9clistenxe2x80x9d automatically, while they are in the standby mode. The control is two-way full duplex, such that there are a plurality of forward control channels (FCC) from the cell to the portable unit (uplink), and a plurality of reverse control channels (RCC) from the telephone to the cell (downlink). A maximum of three channels are assigned to each cell or sector. The cellular units automatically adjust to the best of these channels available in the cell or sector.
There are two possibilities in establishing a cellular conversation:
1) The subscriber initiates a conversation (origination)xe2x80x94the user initiates a conversation from the cellular unit to any telephone subscriber. In this case, he dials the destination subscriber number and presses the send button, and this begins a handshake routine opposite the local cellular cell, which provides service in a given area. The call handling is then passed to an area cellular mobile telephone switch office (MTSO), which checks the information, performs a verification that the subscriber is operating properly, and is entitled to receive service and then connects to the destination subscriber. This process is known as xe2x80x9ccall setupxe2x80x9d.
2) The subscriber receives a conversation (page)xe2x80x94the cellular system receives a request to establish a conversation with a cellular subscriber, and the area cellular MTSO performs a subscriber locate/search activity by sending a xe2x80x9csearch callxe2x80x9d to all the cellular cells (connected to it) and these broadcast it on their control frequencies.
The destination subscribers (when in a standby mode) which are tuned to the local control frequency, respond to the search call and this begins a handshake routine with the area cellular MTSO. When finished, the system assigns a pair of specific frequencies, a forward control channel (FCC) from the cell to the portable unit, and a reverse control channel (RCC) from the telephone to the cell, in full duplex mode, to which the telephone and cell are tuned. Only after this, a ring command is broadcast to the telephone, activating the cellular subscriber""s ringing unit, and this clears the way for a full conversation.
A basic condition in establishing any cellular conversation is that the control frequency and the service in a given area are received by the subscriber with a volume which provides a required signal-to-noise ratio (S/N) or better. Clearly, this condition is also true concerning the receiver equipment at the cellular cell, that is, that the information transmitted by the subscriber is received with the required S/N ratio, or better.
As described above, there exists a need for a device which will prevent the ability to establish a cellular telephone conversation, either received or initiated, in a given area. Various reasons exist for this requirement, and these may be security-related, cultural, moral etc. For example, prevention of a cellular conversation on military bases is a classic security requirement. The same requirement exists in a theater, as a cultural norm in different countries.
Therefore, it would be desirable to provide a device for preventing the establishment of cellular telephone conversations in a given area, for various reasons.
Accordingly, it is a principal object of the present invention to provide a method and device for achieving reliable prevention of cellular telephone calls, within a given area.
In accordance with a preferred embodiment of the present invention, there is provided a method for prevention of cellular telephone calls in a communication system within a given area, said method comprising the steps of:
determining at least one control frequency existing within the area for establishing cellular telephone calls, said control frequency containing information transmitted thereon, said information being transmitted as coded signals and commands; and
generating a signal which interferes with said control frequency by preventing decoding of said signals and commands,
said signal preventing generation of handshake signals in the systems to prevent establishment of a cellular phone call.
In the preferred embodiment, the device and method operate to block the control frequencies of the cellular system within a given area. The device broadcasts a blocking signal with a low power output, which interferes with the reception ability and decoding of signals and commands broadcast at the control frequency. Thus, the handshake routine of the telephone/cellular subscriber with the local cellular system is prevented.
Operation of the device is achieved in several ways, manually, automatically, and/or by remote control. Its operation prevents cellular communication ability by subscribers within the area or within the effective blocking range, which is derived from the effective radiated power (ERP) of the blocking signal, its type and the type of communications/or blocked system.
Using the Inventive device, a given area normally accessible by cellular communications is blocked from such access, thus providing a security-related, cultural or other safeguard. The given area is thereby isolated from cellular communications, and access can only be achieved by physically relocating the user whose cellular telephone has been blocked.
Other features and advantages of the invention will become apparent from the following drawings and description.